Jump to content
Maestronet Forums

How does a violin reproduce overtones? - Theorizing a model


Andreas Preuss

Recommended Posts

  • Replies 646
  • Created
  • Last Reply

Top Posters In This Topic

8 hours ago, uncle duke said:

29 - 11.4     headphones using the websites "3" setting for volume, t.v. blaring in the other room.

ya gee I didn't even think of headphones, duh....I'll try again and see if I get different results, I do think that even small amounts of background noise could alter the results at the extremes...

but I do think this is kinda relevant to listening and or analyzing as an individual, but interesting right off the bat we have differences, which MUST mean that we MIGHT :lol: all hear things differently and that those subtle differences at extreme levels may effect "our" interpretation of quality and the ability to even appreciate the overtones, and subtle harmonics 

Link to comment
Share on other sites

19 hours ago, David Beard said:

One more aspect we don't commonly discuss: capacitance and time lag.

The violin is an energy transducer.  The resonances of the masses hold energy for a while, and have 'capacitance'.

Capacitance takes time both to fill and to empty.

These are real aspects of violin behavior.

capacitance? Like in an electric circuit?

Would it be as easy as 

Capacitance is a function governed by the entire mass?

And how would a violin with low capacitance sound versus a violin with high capacitance?

---------------------

Don't know if this is related to this. I watched the video where Ray Chen plays a 65 dollar fiddle and compares it to a 10 million dollar Strad.

At one point he says that the cheap violin feels for him like 'It wants to continue to vibrate on the same note when I am already on the next'. 

Wouldn't this be a description of high capacitance? 

Link to comment
Share on other sites

5 hours ago, Andreas Preuss said:

Christian doesn't talk about the thickness of his plates. Regardless, with the reinforcement beams carved out of the plate I wouldn't think this is close to a membrane.

A membrane does not have bending stiffness. Maybe a very thin plate behaves membrane like, I do not know. A drumhead or a banjo has a membrane.

Edited by Anders Buen
Spelling correction
Link to comment
Share on other sites

A membrane needs tension to have any acoustic properties.  Violin plates, even extrmely thin, will have their vibration properties determined by bending stiffness and curvature... unless you want to make them flat and super-thin with a pre-tensioned garland like a banjo.  And it would likely sound like a banjo.

Link to comment
Share on other sites

58 minutes ago, Anders Buen said:

A membrane does not have bending stiffness. Maybe a very thin plate bhave membrane like, I do not know. A drumhead or a banjo has a membrane.

 

25 minutes ago, Don Noon said:

A membrane needs tension to have any acoustic properties.  Violin plates, even extrmely thin, will have their vibration properties determined by bending stiffness and curvature... unless you want to make them flat and super-thin with a pre-tensioned garland like a banjo.  And it would likely sound like a banjo.

The Chinese erhu uses a membrane of python skin and it sounds better than many violins.

 

Link to comment
Share on other sites

@Anders Buen, @Don Noon, @Marty Kasprzyk

Need to correct myself.

Of course the violin top is not a membrane like used on drums.

When I am talking of 'membrane' in a violin top I mean 'similar to a membrane' in terms of (almost) uniform thickness. Maybe it is scientific nonsense to talk about an 'arched membrane' since it is not possible to stretch something and have it curved.  However I use this term as an image. The thickness should correspond to the arching with the aim to arrive (in the ideal case) at an even thickness. 

 

 

Link to comment
Share on other sites

3 hours ago, Andreas Preuss said:

capacitance? Like in an electric circuit?

Would it be as easy as 

Capacitance is a function governed by the entire mass?

And how would a violin with low capacitance sound versus a violin with high capacitance?

---------------------

Don't know if this is related to this. I watched the video where Ray Chen plays a 65 dollar fiddle and compares it to a 10 million dollar Strad.

At one point he says that the cheap violin feels for him like 'It wants to continue to vibrate on the same note when I am already on the next'. 

Wouldn't this be a description of high capacitance? 

No. That's a description of high Q and low dampening.

Think of changing fingers right after plugging a string.  Guitarists do this a lot deliberately. Violinists don't normal do this, but I'm we can all remember moments goofing around.

The energy persists, but changes to the new signal.  Capacitance lends a persistence of energy, not necessarily of signal.

It is high Q resonances that want to keep energy at their pitch, instead of responding to a driving signal.  

 

Link to comment
Share on other sites

3 hours ago, Andreas Preuss said:

@Anders Buen, @Don Noon, @Marty Kasprzyk

Need to correct myself.

Of course the violin top is not a membrane like used on drums.

When I am talking of 'membrane' in a violin top I mean 'similar to a membrane' in terms of (almost) uniform thickness. Maybe it is scientific nonsense to talk about an 'arched membrane' since it is not possible to stretch something and have it curved.  However I use this term as an image. The thickness should correspond to the arching with the aim to arrive (in the ideal case) at an even thickness. 

 

 

I think Dons explanation is correct. A membrane is a 2D version of a string. It needs tension as Don mentiones, to produce sound and have a pitch. Like stretched strings, a membrane have harmonic resonances (I believe). The mode shapes are different though than just a string as some is 2D. An intereaction with the air under the membrane may also play a role, like it probably does for the Erhu. 

Link to comment
Share on other sites

2 minutes ago, Anders Buen said:

I think Dons explanation is correct. A membrane is a 2D version of a string. It needs tension as Don mentiones, to produce sound and have a pitch. Like stretched strings, a membrane have harmonic resonances (I believe). The mode shapes are different though than just a string as some is 2D. An intereaction with the air under the membrane may also play a role, like it probably does for the Erhu. 

Question, lets say we have this membrane, and it's somewhat like a floppy thin pizza dough unbaked and then lets say instead of stretching it over some frame and then exciting the stretched skin somehow, that instead it is held at two points , as if one were holding a wet towel , pinching it with their two hands at the very edge, and then we introduce airflow, so the membrane/ sheet starts to "waffle and flap" , this "flapping" sound, is it a form of breaking that "law" or a different version of it? say the characteristics of a open gong being hit vs a stretched drumskin?  Meaning are two points of loose contact considered "tension" and is flapping "sound" or noise ? as compared to exciting the same membrane stretched over a frame.

 

I often think about what happens when vibrations meet the physical end of the road as they meet the "event horizon" of the nodal outer edges of the plates and if there isn't some "flapping./whip cracking" energy effecting the air at the very outer edges of the instrument. Where the violin itself basically acts like a "micro hyper flapping two tier 2d membrane" and that those "energy outputs" are a byproduct of the initial input but somewhat of a separate "activity/dimension of sound" that operates within or just outside of the confines of the 3d structure.

 

Link to comment
Share on other sites

5 hours ago, Andreas Preuss said:

@Anders Buen, @Don Noon, @Marty Kasprzyk

Need to correct myself.

Of course the violin top is not a membrane like used on drums.

When I am talking of 'membrane' in a violin top I mean 'similar to a membrane' in terms of (almost) uniform thickness. Maybe it is scientific nonsense to talk about an 'arched membrane' since it is not possible to stretch something and have it curved.  However I use this term as an image. The thickness should correspond to the arching with the aim to arrive (in the ideal case) at an even thickness. 

There has to be an optimal thickness for a violin belly based on arching and the spruce quality and characteristics, but does the rest of the instrument need to be light in weight? 

For example, electric guitars are heavy for a reason, better resonance, tone and sustain. How much of this is applicable to the body of a violin?

 

Link to comment
Share on other sites

59 minutes ago, jezzupe said:

I often think about what happens when vibrations meet the physical end of the road as they meet the "event horizon" of the nodal outer edges of the plates and if there isn't some "flapping./whip cracking" energy effecting the air at the very outer edges of the instrument. Where the violin itself basically acts like a "micro hyper flapping two tier 2d membrane" and that those "energy outputs" are a byproduct of the initial input but somewhat of a separate "activity/dimension of sound" that operates within or just outside of the confines of the 3d structure.

I think that you're thinking yourself into a tizzy.  Assuming the edges of the plate are rigidly held (which is definitely not true at some of the lower frequencies), then it is a node, and by definition nothing is moving there.  It's like a 2D version of a string in some ways, and there's not much whip cracking hyperflapping at the nut when playing an open string.

Link to comment
Share on other sites

5 hours ago, Andreas Preuss said:

@Anders Buen, @Don Noon, @Marty Kasprzyk

The thickness should correspond to the arching with the aim to arrive (in the ideal case) at an even thickness. 

There is no ideal anything in violins, except in the mind of the maker.  These kinds of "ideals" I think are more of a barrier to finding things that actually work.  (Trying to keep M2 and M5 exactly an octave apart is one example)

Link to comment
Share on other sites

4 hours ago, Don Noon said:

There is no ideal anything in violins, except in the mind of the maker.  These kinds of "ideals" I think are more of a barrier to finding things that actually work.  (Trying to keep M2 and M5 exactly an octave apart is one example)

Completely agree.

What I am trying to say is just by the experience I have accumulated so far, a top plate with minimal thickness variations works better than with big variations. And this can be seen as related to the arching. ‘Ideal’ is in this sense for me an ‘general idea model’.

In any case I am an advocate to adjust those parameters to the wood properties. Since each piece of wood is different I like flexible methods best. 
 

For back plates I made things like immerse a back for 48 hours in water and the result for the arching was a kind of uncontrollable, but I think this works better than trying to control everything. (Hence I am not really a fan of doing things with CNC.)

 

Link to comment
Share on other sites

5 hours ago, sospiri said:

For example, electric guitars are heavy for a reason, better resonance, tone and sustain. How much of this is applicable to the body of a violin?

Electric guitars need this for the electronic amplification. It seems some electric violins are made on similar principles, this means just cut off whatever resonances they could produce on their own.

Nevertheless, I see in violin making some sort of 2 basic concepts. One which works with a heavy and rather unflexibel back and ‘heavy’ ribs (like GDG) and the other with a more flexible back and light ribs ( like Strad).

I heard from a guitar guy that there is a maker of acoustic guitars who makes an unusual heavy and inflexible rib garland on his guitars with big success. 
 

My experiments on the new concept violin could at the initial stage improve things a lot mwith reinforcing the linings. And further experiments showed bigger tonal changes by changing only rib properties. (Not saying that this is everything) I think there is a lot to discover, but I can’t say if this applies for traditional Strad or GDG model violins as well. 

Link to comment
Share on other sites

13 hours ago, Anders Buen said:

A membrane does not have bending stiffness. Maybe a very thin plate behaves membrane like, I do not know. A drumhead or a banjo has a membrane.

One might ponder if Cremonese violin makers didn’t try to get as close as possible to a ‘membrane like violin top’.

Link to comment
Share on other sites

3 hours ago, Andreas Preuss said:

Electric guitars need this for the electronic amplification. It seems some electric violins are made on similar principles, this means just cut off whatever resonances they could produce on their own.

Nevertheless, I see in violin making some sort of 2 basic concepts. One which works with a heavy and rather unflexibel back and ‘heavy’ ribs (like GDG) and the other with a more flexible back and light ribs ( like Strad).

I heard from a guitar guy that there is a maker of acoustic guitars who makes an unusual heavy and inflexible rib garland on his guitars with big success. 
 

My experiments on the new concept violin could at the initial stage improve things a lot mwith reinforcing the linings. And further experiments showed bigger tonal changes by changing only rib properties. (Not saying that this is everything) I think there is a lot to discover, but I can’t say if this applies for traditional Strad or GDG model violins as well. 

But what is being amplified in an electric guitar? It is the movement of the strings, which is influenced by the construction. Why is a Gibson Les Paul heavy and not light?

Is a light back and neck better on a violin? 

About the ribs, does a violin move in a 2 dimensional figure of 8 at certain frequencies? If so what is the influence of the shape of the ribs, linings and blocks?

2 hours ago, Andreas Preuss said:

One might ponder if Cremonese violin makers didn’t try to get as close as possible to a ‘membrane like violin top’.

Probably. They must have thought about it. But if we ask the question of speaker cone thickness, what is the ideal? It seems there isn't one. So doesn’t the same thing apply to plate thicknesses? There is too light and too heavy, but no ideal weight/thickness?

Link to comment
Share on other sites

2 hours ago, Andreas Preuss said:

One might ponder if Cremonese violin makers didn’t try to get as close as possible to a ‘membrane like violin top’.

Just change your word to diaphragm, skip the issue of implied stretching.

In a membrane or a string, it's implied that the restoring force comes of an elastically stretched material.

In a rod or diaphragm, the restoring force comes from the elastic stiffness of the material.

 

 

 

 

Link to comment
Share on other sites

10 hours ago, jezzupe said:

Question, lets say we have this membrane, and it's somewhat like a floppy thin pizza dough unbaked and then lets say instead of stretching it over some frame and then exciting the stretched skin somehow, that instead it is held at two points , as if one were holding a wet towel , pinching it with their two hands at the very edge, and then we introduce airflow, so the membrane/ sheet starts to "waffle and flap" , this "flapping" sound, is it a form of breaking that "law" or a different version of it?

I reality a string or a mylar drumhead or bajo mambrane does have some bending stiffness, although the effect of it is neggigible in copmarison to the tension effect. A baked pizza does have more bending stiffness than before baking it. There are many such «between the ideals» in nature. When we or somebody look at problems mathematically, it is usually done by simplifying the problem including the most important effects. 

Link to comment
Share on other sites

6 hours ago, Anders Buen said:

When we or somebody look at problems mathematically, it is usually done by simplifying the problem including the most important effects. 

For most violin analysis, I see that the problem is simplified to what can be measured or calculated... which EXcludes many of the most important effects.  The critical higher frequencies are just too complex to deal with in an analytical way.

Link to comment
Share on other sites

3 minutes ago, Don Noon said:

 The critical higher frequencies are just too complex to deal with in an analytical way.

At least in the articles it appears pretty simple. E.g. the effect of the bridge in Jim Woodhouses article on the bridge hill. Also in building acoustics the radiation from plates in the highs is pretty simply described and it works well for sound insulation calculations, and measurements, at least.


The role of damping on the critical frequency e.g. In plate theory the damping only has an effect around the critical frequency and above. For modal behavior, disregarded in plate SEA-theory (often used in building acoustics because it works), it affects the height of the peaks and valleys. In sound insulation measurements we see that the critical frequency of 13mm gypsum boards appear as a dip in the 2,5 kHz range, steady, or in flanking transmission problems (the sound follow the plates around the wall, if the plates are not cut. 


It becomes a bit more complicated when the plates are more dissimilar in the length and cross direction as for wood. 
 

I am a different animal in this respect, with the occupation I have. I do have an old article draft on this theme, but haven't finished it. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.



×
×
  • Create New...